Don Esker has wanted to work with fossils since he was 4 years old. "My first polysyllabic word was dinosaur," says the in situ curator of the Mammoth Site in Hot Springs, S.D. To map a bone at the indoor dig--a 26,000-year-old sinkhole that contains the remains of more than 50 mammoths--Esker snaps a picture of it, then uses surveying equipment to determine its coordinates. His duties include explaining his job and what he's learned to schoolchildren who visit the site. "Each kid is an excellent scientist in potential," Esker says. "If we can encourage them to maintain that enthusiasm, then we've done our job."